Why won't a drill do it? I'm usually able to get round holes for connectors by drilling a pilot hole and enlarging the hole about 1 mm at a time until I reach the target diameter. For DIY that works just fine.

For bigger diameters (approaching 1/2" and larger) I use a stepped drill. Works well.

Punches are expensive, but it pays to get a good one.

For IEC connectors, I drill a hole in each corner and use a coping saw to make the opening. Then a small file until the hole has the desired shape. It's worked well so far...

I used a center punch to align and still not good aliment on a manual drill.
Question is basically, even thought I'm good with tools, I'm not getting professional results.
I'm just asking what is needed, for example If I was going to do a few to sell. The small scratches and imperfections won't allow to get good price.

Also would like mine to be perfect

Where can we get good chassis cases (like the ones in Pass Labs, Music Hall and Shanling use [with thick front plate])?

do you protect the surface when you are working on it ? I always use painters masking tape.

__________________"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.

Try Greenlee metal punches. Good for thin mild steel and aluminum up to 1/8". I've used them with perfect results. You drill a pilot hole for the punch bolt and crank a wrench to push the punch through(or spend the big bucks and get a hydrolic punch.

You know what, I bought a set of those stepped drill bits but I always forget to use them. I just did some AC and speaker connectors. Used a drill to get a hole big enough to insert a file. And just filed the cr***P out of it. You can make a BIG hole with a file in about 15 minutes, just takes a lot of elbow grease and care. Of course they look bad when you remove the connector (can't tell with the connector on there).

If even a neat hole with a nice drill is not good enough for you, why don't you use someone like frontpanelexpress.com? Design your panels and holes on a PC and email it off. The panel is CNC drilled, engraved with ink filled lettering. Looks nice.

__________________
Retired from DIY (2010) but still lurking now and again. My DIY audio projects- PartTimeProjects.com.

In sheet metal I always drill a little undersize and clean up with a rat tail file. (round). A file handle really help you with control. If you are doing something like switches or fuse holders that are D shaped, drill 1/32" undersize and finish the D shape with the rat tail file. Round Greenlee punches start at about $40 for the 5/8" style, and they don't have the weird shapes of switches and fuse holders at home depot or mcmaster.com. For square holes, I drill 4 holes undersize and saw in undersized with a sabre saw (32 tpi) then finish out to full size with a diamond dust bit from Harbor freight (about the only good tool they sell) in an air die grinder. Protect surface with masking tape. Wear Safety glasses
If your drill walks off center, stop and recenter the hole with a carbide tree bit (I use 5/16") tree bit. They have a pointy end and are easier to control in a drill than a 135 deg point bit. Then finish with the undersized regular drill bit. I don't use stepped bits, too difficult to re-sharpen. .